Steam generation and superheating



Nov. 29, 1932. J, E, BELL 1,889,031

STEAM GENERATION AND SUPERHEATING Filed Jan. 15, 1925 6 Sheets-Sheet l Nov. 29, 1932( J. E. BELL STEAM GENERATION AND SUPERHEATING .Filed .JamQ 6 Sheets-Sheet 2 IIFIIIIIIIIII NUI ' 1N VENTO/e v70/WV EAU MfS/WW TTORNEY Nov. 29, 1932. 1, BELL 1,889,031

STEAI GENERATION AND SUPERHEATING Filed Jan. 13, 1923 6 Sheets-Sheet 3 /N VEN TOR v @HA/727544 BVM www A TTORNE Y Nov. 29, 1932. J. E, BELL STEAM GENERATION AND SUPERHEATING Filed Jan. 13, 1923 6 Sheets-snee?. 4

D @/@QQQQQ Nov. 29, 14932e J. E. BELL STEAM GENERATION AND SUPERHEATING Filed Jan. 15. 1923 6 Sheets-Sheet 5 OO O0 0000 DDD @non nnmp ,11131 Nm. 2,9, 193.2. J. E, BELL. 1,889,031

STEAM GENERATION AND SUPERHEATING Filed Jan. 13, 1925 6 Sheets-Sheet 6 Patented Nov. 29, 1932 UNITED STATES PATENT OFFICE JOI-IN E. BELL, OF BROOKLYN, NEW YORK; LOLA RUST BELL, OF JACKSON' HEIGHTS, NEW YORK, EXECUTRIX OF SAID JOHN E. BELL, DECEASED, ASSIGN'OR TO lFOSTER WHEELER CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEXV YORK STEAM GENERATION AND SUPERHEATING Application led January 13, 1923. Serial No. 612,448.

My present invention consists in novel methods of, and improved apparatus for effecting the combustion of fuel and utilizing the heat generated, and was primarly devised, for generating and superheating steam under high pressure with heat evolved by the combustion of comminuted fuel burnt in suspension with the maximum efficiency. The invention comprises improvements in construction; and in the relative arrangement of furnace.l boiler, superheater, econoniizer, and air preheating elements; and in the mode in which combustion is effected and the available heat utilized; all devised with the genn eral object in view of securing efficient combustion, and efficient utilization of the heat evolved, in apparatus, which, as a Whole, is compact 'and of relatively large capacity for its bulk, and is relatively inexpensive to construct and maintain.

The invention is characterized by the provisions made for utilizing the metallic Water and steam cooled heat` absorbing parts or other heat utilizing apparatus, to protect the furnace housing against the high temperature prevailing in the combustion chamber and to avoid destructive effects from the nongaseous residue of the fuel When the latter is powdered coal. To this end the interior Walls of the combustion chamber proper, or at least the portions of said Walls enclosing the high temperature zones of the chamber, are either formed by, or are arranged to be cooled by radiation to the useful heat absorbing surface of the boiler or other heat utilizing apparatus.

In the preferred superheater boiler construction illustrated the means employed to guide the flame through the path necessary for complete combustion, and to fully sweep the heat absorbing surfaces exposed in the furnace, and to precipitate slag or ash formed, comprises a central suspended baffle, constructed with, and supported by tubes, hea ders and drums cooled by either the Water of circulation in the boiler or by steam in the process of being superheated, the cooling members supporting refractory shapes whereby the baffle is made tight. This baffle is preferably disposed as shown to define a gas flow or fiame path of U-shape, With provisions for supplying fuel and the air for its combustion to the combustion chamber at the top of one leg of the yU-shapcd path, and for withdrawing gaseous products of combustion from the combustion chamber proper at the top of the other leg of said path. This makes it possible to provide a flame path in the furnace chamber of sufficient length and sufficiently restricted in transverse cross section to effect rapid ignition and efficient combustion of the fuel with a minimum of excess air. lVith this arrangement the boiler heating surfaces utilized to forni or protect the housing wall and to form the above mentioned baffle, absorb a relatively large por-tion of the heat evolved by radiation, and absorb additional heat by Contact With the highly heated burning gases and products of combustion. T he heating' gases which leave the combustion chamber proper at a relatively high temperature are utilized in the preferred form of apparatus illustrated, to supply heat to additional boiler heating surface so arranged as to insure a relatively high rate of heat transfer, so that a boiler constructed in accordance with the present invention is characterized by its high capacity per unit of volume. The boilerproper is advantageously associated in a novel and compact manner with an economizer and air prehcater for utilizing the available heat in thc heating gases leaving the. boiler proper.

In the preferred mode of carrying out my invention, the fuel is introduced into the combustion chamberat a velocity appreciably above that at which the gaseous products of combustion escape from the combustion chamber, and the air necessary for the coinbustion of the fuel is supplied adjacent the fuel inlet and in part at an angle to the entering stream of fuel and air so as to insure a relatively quick or short clear flame combus tion, with consequent high fiame temperature and rapid heat absorption by radiation. Advantageously the elongated flame path .increases in transverse cross section to prevent objectional increase in gas velocity as combustion proceeds and the volume of the gases increase. Advantageously also the final portion of the combustion chamber decreases in transverse cross section to eliminate or desirably minimize any reduction in gas velocity as the heating gases contract in consequenee of the heat given up by them to the heat utilizing apparatus.

a better understanding of the invention, however, and its advantages, reference should be had to the accompanying drawings and descriptive matter in which ll have illustrated preferred embodiments of my invention.

Uf the drawings:

Fig. l is a sectional elevation of a preferred construction Fig. 2 is a section on the broken line 2--2 of Fig. l;

Fig. 2A is a partial section 2A-2A of Fig. l;

.. Fig. 2B is a partial section on the line 2B-2B of Fig. l;

Fig. 3 is a section on the line 3-3 of Fig. l;

Fig. /1 is a partial section on the broken line 4-4 of Fig. 1;

Fig. 5 is a sectional elevation illustrating a modified portion of the apparatus shown in Fig. 1;

Fig. 6 is a sectional elevation illustrating another modified portion of the apparatus shown in Fig.y l;

Fig. 7 is a sectional elevation illustrating a modified boiler construction;

Fig. 8 is a partial section on the line 8-8 of Fig. 7

Fig. 9 is a partial section taken similarly to Fig. l illustrating another modification; and

Fig. 10 is a section on the line 10-10 of Fig. 9.

ln the construction shown in Figs. l to 4, A represents the combustion chamber of a furnace, which, as shown, has its housing Wall formed of an outer metallic framework and a lining of fire-brick or analogous refractory material except in portions of the housing in which the wall is formed in whole or in part by portions of the boiler and the steam superheaters. The powdered coal or analogous fuel, and a relatively small portion of the air for its combustion are passed into the top combustion chamber through downwardly projecting nozzles B from feeding mechanism (not shown) which may be of any usual or suitable type. Each nozzle B as shown is surrounded by an air supply easing C carried on the top wall of the boiler housing adjacent the front edge of the latter. Preheated airis supplied to the casing C through branch pipes C from a bus pipe or air flue C2 running along the front end and sides of the boiler housing, and coimected at its ends to an air .preheater located at the rear of the boiler and hereinafter de- 'on the line scribed. The flue C2 also supplies air to the combustion chamber through a row of ports Av in the front wall of the boiler housing, and through ports A2 in the side walls of the housing. v

rllhe boiler proper comprises a steam and' water drum D located at thetop of the combustion chamber A, approximately midway between the front and back ends of the latter. Circulating tubes D inclined slightly down ward from the horizontal lead from the opposite sides of the drum to front and rear headers D2 and D3, respectively. Vertical water tubes D4 connect the headers D2 to a drum D5 adjacent the lower end of the combustion chamber proper. As shown there are two rows of tubes D, with the tubes in the two rows staggered, which form a screen located away from the inner side of the front wall of the boiler housing which both reduces the heat absorption of the latter, and cools it by absorbing radiant heat. Two rows of vertical tubes D40 connect the headers D3 to drum D6 shown as located at the same level as the header D5, and forms a screen spaced a short distance in front of the rear wall of the combustion chamber A, and protecting that wall, as the tubes D4 screen protect the front wall. As shown the top of the boiler housing is formed in part by refractory tiles mounted on the tubes D. Fach of the drums D5 and D6 is connected to a drum D9 located at a lower level and directly beneath the drum D by a set of straight tubes D7, and by a set of curved tubes D8 staggered with respect to the tubes D. The tubes D7 and D8 form a cooling screen for the bottom wall of the furnace chamber through which ashes and slag pass down into the pockets or ash pits A.

Depending from the drum D is a hollow baffle formed by a drum D11, bent tubes D1o and straight tubes D13 'and tiling D. rl`he drum D11 is located directly between the drums D and D9. There are two rows of bent tubes D1", the tubes in one row being connected at their upper ends to the drum D at the front side of the latter while the tubes in the other row are connected to the drum `D at the rear side of the latter,the tubes in both rows being connected at their lower ends to the drum D11. the tubes D at each side of the drum D are connected to the latter through a corresponding hollow rib D12 riveted to the drum D and connecting with the latter through ports D121 (see Fig. 4). The drum D is also connectedv to the drum D11 by a central row of tubes D13. rFhe tubes D13 are straight vertical tubes radially disposed with respect to the drums D and D11 which they connect. The tiling E unites with each row of tubes D10 to form a bathe wall. The baille wall thus formed by As shown the tubes D1 and l B. The drums D11 and D9 are connected at each end of the furnace by external conduits or water legs D15.

The burning gases and products of combustion leave the combustion chamber A proper, through a port Aa'in the rear Wall of the latter running the fulll length of the furnace immediately beneath the header D3, and thence pass downward through vertical channels A4 in a body of suitably refractory material as cast iron, or brickwork as shown. Centrally disposed in each channel A4 is a boiler tube D11 which does not ill the channel, thus providing a heating gas flow path which is annular in cross section, between each tube D14 and the wall of the corresponding channel A4. The tubes DM are connected at their upper ends to the headers D3, and are con- :nected at their lower ends to headers Dso which are located at the level of, and are connected to the drum D6.

The gasses issuing from the lower ends of the channels A4 enter the lower chamber F of two similar economizers F through which the gases pass upward past horizontally disposed economizer tubes F2 which advantageously consist of steel tubes encased in tubular corrugated cast iron casing sections. Preferably the tubes F2 of each economizer are connected, so that the water to be preheated enters the tubes F2 in the top row through a suitable inlet header F3, and thence flows serially through successively lower rows of tubes and the head-ers F4 by which each tube in an intermediate row is connected at one end to a tube or tubes in the row above it, and is connected at it-s opposite side to a tube or tubes in the row beneath it. The outlet header F5 of each economizer is connected to the boiler circulating system as by means of conduits F leadingto the steam and water drum D. Spray pipes F7 may be provided as shown for cleaning the economizer tubes from time to time, by washing them with water.

From the top space of each economizer, the heating gases pass through the outlet F8 into the upper end of a corresponding air preheating chamber G which, as shown, comprises a plurality of 4thin air chambers or flattened tubes G, spaced apart to provide channels G2 through which the heating gases pass downward through the air preheater to conduits H running to the inlets of the exhaust fan H Air is blown into the lower endsof the chambers or flattened tubes G by the forced draft fan J, and passes from the upper ends of the tubes or channels G of each heater vinto the top chamber G3 of the latter. The top chamber G3 of each air heater has an end portion G4 connected to the corresponding upturned end portionof the air iue C2. I

Incorporated in the side walls of the combustion chamber are superheater units K; As shown there are four such superheater units, two in each side wall, one in front, and the other back of the baffle depending from the drum D. Each superheater unit comprises an upper inlet header K an outlet header K2, bot-h outside' the boiler housing proper, and tubes K3 connecting the headers K. The tubes Ka have straight body portions located wit-hin the boiler housing and encased in cast iron casing sections K4, which unite to form a continuous metallic wall receiving radiant heat from the combustion chamber by contact with the burning gases and products of combustion, and transferring heat thus absorbed to the tubes K3 by conduction. Each of the tubes K8 is formed with transverse end portions K5 extending horizontally through the housing wall, and each connected int-o the corresponding header K or K2.

In the contemplated method of use of the apparatus shown in Figs. l to 4l, the coal is projected into the combustion chamber through the nozzles B in a blast of carrying air. Each jet of fuel and carrying air thus entering the combustion chamber is surrounded by an envelope of preheated a'ir supplied through the corresponding casing C, and the additional air required for the combustion of the fuel is supplied through the distributed ports A and E. Owing to the relatively restricted horizontal cross section of the upper portion of the U-shaped path into which the fuel and air for its combustion is introduced, and the manner in whichthe air supporting combustion is supplied, rapid mixing of the fuel and consequently rapidv combustion is had, notwithstanding the relatively high flow velocity of the order of 100 feet per second or so, with which the fuel jets enter in the combustion chamber, and the relatively high velocity of gas flow necessarily maintained throughout the combustion chamber in order -to obtain the high capacity per unit of volume which I can, and intend to secure with the apparatus disclosed. While the flow velocities through the various portions of the combustion chamber may vary through wide ranges in the practice of my invention, I will state by way of illustration and example, that the particular apparatus shown in Figs. l to 4 was primarily design-ed for operation under conditions requiring an average flow velocity through the downflow leg of the U-path at levels immediately beneath the tops of the superheater in the neighborhood .ofv50 feet per second, to carry the normal boiler load.

In the preferred mode o f operation contemplated by me, the carrying air will form something like 3 or 4 per cent of the total volume of air supplied to-support combustion, and something like 10 to 15 per cent of the total volume of air will be supplied from the air flue C2 through the branches C and casings C. The rate at which combusiou 1s substantially completely depends, to a large degree therefore, upon the manner in which the air supplied to the ports A and E 1s mixed with the fuel, and may be varied by changing the location and disposition of these ports, and in particular, may be retarded by increasing the area of the ports and. consequently reducing the velocity of a1r f low therethrough, or by increasing the vertical distance over which the ports are distributed. In the practice of the invention l consider it advisable, however, to so arrange the ports A and E that the air discharged by them into the combustion chamber will mix very rapidly with the fuel and a very intense combustion will occur in the portion of the combustion chamber immediately below the level ofl these ports.

T he rapid combustion thus secured, the fact that ordinarily not more than 1.0 to 15 per cent of excess air is required, and 6the fact that the great volulne of air supplied is preheated by its passage through the air heater G, result in relatively high temperatures of combustion. The high temperatures thus produced, markedly increase the heat transferred to the heating surfaces exposed to radiation, as Well as by contact with the highly heated gases.

The fact that the furnace housing wall and central baille are protected by the boiler and superheater surface, incorporated in, or screening them, 'prevents the wall and baille from being overheated, and prevents them from being injured by the erosive action of the none-gaseous residue of the powdered fuel, as this residue is cooled by or before contact with the housing wall and baille below the temperature at which it will run down them in molten form. The tapered form of the central baille, and its disposition results in an increase in the horizontal cross sect-ion of the gas path from the top to the bottom of the leg of the path in which combustion is initiated in more or less close corespondence to the increase in volume of the air and products of combustion, resulting from their increase in temperature, and a reduction in cross section in the other leg, corresponding to the decreasing volume of the ascending gas as the latter cools.

With the rapid reversal in vertical velocity, occurring as the burning gases sweep around the lower end of the baille, a very considerable portion of the non-gaseous residue of the fuel' settles down into the ash pits or pockets A, and is cooled as it passes through the cooling screen formed by the tubes D7 and D8, so that it collects in the ash pit mainlyin the form of sandy ash and solidified granules,

which can be removed from the ash pits by superheaters below the drum D are not as thoroughly protected as other parts of the boiler housing, but the protection which they receive against overheating from the internal boiler and superheater parts will ordinarily be sufficient. The portions of the end walls of the housing not directly screened by, or incorporating boiler or superheating surface, may be reduced in area to any desired minimum by a suitable design and disposition of parts, or such portions may be cooled by external portions of the boiler or superheater, orby providing air preheating channels in the furnace wall itself. In the construction shown in Figs. l to 4, the portions of the boiler side walls along which the air flue C2 and the water legs D15 extend may be thereby substantially cooled if the parts are proportioned and arranged with that end in view.

The .fact that the furnace housing walls in the described construction are protected against the eresive action of the non-gaseous residue of the fuel, and are maintained at moderate temperatures by the adjacent boiler and superheater parts, permits of the use of a housing wall less thick andless expensive to construct than would otherwise be required; especially as the comparative coolness of the walls makes thickness unnecessary to prevent excessive heat losses by eX- tern al radiation. The invention thus reduces the initial cost of construction; and what is more important, it eliminates the necessity for the frequent rebuilding of boiler housing walls, which is characteristic of the operation of ordinary modern high capacity boiler furnace plants.

The straight tubes D1? connecting the drumsD and D11, are protected' from the high temperatures in the combustion chamber proper by the tubes D10 and tiling E, and in consequence afford relatively cool paths of comparatively small flow resistance for the downflow of water from the steam and water drum D into the drum D9 necessary to maintain the rapid upflow of steam and water through the tubes D10, and through the tubes D7, D3, D4, D4", and D14 to which water passes from the drum D11 through the external water legs D15 and drum D9. The staggered arrangement of the tubes D* and D4", in the two rows of each set of these tubes, permits the tubes in the outer row of each set to receive an adequate portion of the radiant heat.

`With the described arrangement, operated in the manner contemplated by me, the heating gases will leave the combustion chamber through the port A2 and will enter the refractory channels A4 at a high temperature which may in some cases be in the neighborhood of 1800o F. The passage of the heating gases through the annular spaces formed, one between the curved wall of each channel A4 and the boiler tube D14 centrally disposed therein, will insure a very high rate of heat transfer to the tubes D24, for the latter Will receive heat not only from the gas by contact therewith, but by radiation from the inner Walls of the channels A4. Assume, for example, that the temperature within the tubes D14 is 400 F. or thereabo-uts, and that the gases enter the tops of the channels A4 at a temperature of 18000'. The 4brickwork of course would tend to approximate the temperature of the heating gases unless provisions were made for rapidly withdrawing heat from the brickwork. lVith the described construction, the brickwork is effectively cooled by the tubes D14 which absorb heat so rapidlyv from the brickwork that the temperature of the hotter ends of the Walls of the channels A4 Will be in the neighborhood of 1000 or 12000.With an entering gas temperature of 180OOF. As a result of the high heat transfer rate obtainable in the portion of the boiler Within the combustion chamber, and in the boiler extension formed by the tubes D, the normal economical load capacity of the boiler may Well be ten or more times the nominal rating based on 10 square feet of heating surface per boiler H. P. The single longitudinal pass formed by the tubes D14 may be made quite as effective, with the same character of draft loss therein, as a plurality of transverse passes such as are illustrated in Figs. 7 and 8 across the same number of tubes and is inherently more compact as it eliminates the space at each end of the tub-e bank shown in Fig. 7.

' The economizer and air preheater illustrated insure an efficient utilization of the available heat in the gases leaving the boiler proper in apparatus unusually compact in form, and requiring relatively lovsT head Cil room. rlhe air heated in the preheater G is efficiently utilized in the combustion chamber A, and substantially increases the etliciency of the plant as a Whole, since the air thus preheated forms the great bulkof the air required to support combustion. The preheatng of air supplied for combustion directly and substantially increases the tempcraure in the combustion chamber, and thereby increases the rate of heat absorption by the superheater and by the portion of the boiler Within the combustion chamber, and thus increases the efliectiveness of the apparatus in this manner, as Well as by aug- In the boiler shown in Figs. 1 to 4, the headers D2 are in the form of double boxes each having a partition Wall D17 in the center and each having four tubes D4 connected into it. At the front end of the boiler, the tubes D -are spaced twice as far apart as at 'the rear gle large steam and Water drum D of the constructon first described may advantageously be ireplaced by a multiplicity of small drums as in the construction shown in Fig. 6, Where there are four such drums DA, DA, DA2, and DAS. The tubes D13 are connected to and extend radially downward from the drum DA. The drum DA is located directly above the drum DA and is connected to the latter by short tubes D21. The drums DA2 and DM are placed in front and to the rear of the tubes D2'1 With their axes intermediate the levels of the axes of the drums DA and DA. The drums DA2 and DA3 are each connected to the drum DA by a corresponding set of straight tubes D22 and are each connected to the drum DA by a corresponding set of b-ent tubes D23. Y

It Will be readily apparent, of course, to those skilled in the art, that many changes may be made in the form of the apparatus disclosed in addition to those referred to above, by Way of example; and in some cases it may Well be desirable toemploy some of the special features of construction and arrangement embodied in the apparatus shown in Figs. l to 4, While omitting others, for example, in Figs. 7 and 8, I have illustrated a modification of the apparatus shown in 1 to 4 in Which the economizer and air preheater are omitted.

In Figs. 7 and 8, the combustion chamber AA proper has a screen Wall composed of a single roW of Water tubes D41 at the front, and at the rear of the combustion chamber, and these tubes are directly in contact with the inner surface of the housing Wall proper. The tubes D4 are connected to a steam and Water drum D, through tubes D and headers D25 and D26 corresponding generally in location and purpose to the tubes D and headers D2 and D2 respectively, of the construction first described. At their lower ends the front row of tubes D41 are connected to a header D27 Within the combustion chamber from Which a row of inclined tubes D20 extends across the bottom of the combustion chamber to an external header D28 which is connected at each sde of the boiler to the steam and water drum D through piping 0. rl`he rear row of water tubes D41 are connected at their' lower ends to external headers D10 and D30, and through piping 0 at each end of the boiler', to the drum D. From the combustion chamber proper, the heating gases pass into the upper of three horizontal transverse passes across a band of vertical water tubes connected at their upper ends to the headers D20, and connected at their lower ends to the headers D11. These passes are defined by transverse baiiles P and F2, and b y a vertical batile l? composed of tiles located between the two rear rows of tubes D, andextending from the headers D10 to the upper transverse baiile P. At the right of the bank of water tubes D31, as seen in Fig. 7 is a row of Vertical water tubes D03, which are substantially larger in diameter than the tubes D31, and are connected 'at their upper ends to a header D31 which is connected at each end of the boiler to the drum D by a piping 00. rlhe tubes D13 are connected at their lower ends to a header D10, and the latter is also connected by tubes D3G to the headers D. From the bottom of the boiler extension the cooled heating gases pass through the conduit HA to the inlets of the exhaust fan H.

ln Figs. 7 and 8, the air supporting lcombustion is not preheated, but is supplied to the combustion chamber AA through the inlets A and A2 directly from the atmosphere. rlhe hollow baffle suspended from the steam and water drum D in Fig. 7 is essentially thesarne as that shown in Fig. l, eX- cept that the tubes D100 corresponding to the tubes D10 of the construction first described, are shown as straight tubes and the header D110 to which the lower ends of the tubes D100 and D13 are connected, is a flattened boxlike header, covered at its sides and bottom by tile or other insulating material D111. lln Flg. 7, a single superheater 1s provided 1n each side wall, and extends the full depth of this wall.

As a general proposition it is immaterial whether any particular portion of the housing wall of a superheater boiler is formed or screened by steam or water cooled portions of the boiler heating surface, and in the claims appended to this specification, the term boiler heating surface is used generically to include superheater surface as well as water cooled surfaces of the boiler proper. ln some cases however it may be desirable to employ superheater surface as distinguished from boiler surface proper in the construction of the battle, as illustrated in Figs. 9 and 10 wherein the baiiie structure comprises two sets of l superheater tubes K10 corresponding in general arrangement and disposition to the tubes D10 of the construction first described. The tubes l 10 are all connected at their lower ends to a superheated steam outlet header K11.

asaaosi The tubes K10 in each set are connected at their upper ends to a corresponding header K11, which may besupported in any suitable manner, and as shown, is located immediately above the corresponding row of tubes D. Steam is supplied to the headers K12 through connections K13 from the drum D which aretions, and project outwardly beyond the eX-,

posed faces of the latter. .Elements K10 in the form of angle bars or the like are advantageously placed atthe inner side of each superheater tube.- The lower bent ends of the tubes K10 support specially shaped tile K17 which protect these bent end portions of the tubes and the header K11 against direct heat radiation from the furnace chamber. rllhe ports K18 employed to pass air for combustion from the interior of the baffle into the furnace chamber are formed, in the construction illustrated in Figs.l 9 and 10, by omitting corresponding shadow brick K11".

While the furnace constructions illustrated were primarily designed for use with powdered coal as the fuel, and possess special advantages for such use in that they eliminate or substantia'ily minimize troubles from the non-gaseous residue of the fuel burned, the

furnaces are well adapted for use with little or no change in burning oil or gas` instead of powdered coal.

While in accordance with the provisions of the statutes, ll have illustrated and described the best forms of my invention now known to me, it will be apparent to those skilled in the art, that changes in form may be made without departing from the spirit of my invention as set forth in the appended claims, and that some features of my invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention, what ll claim as new and desire to secure by Letters Patent, is:

1. rllhe combination in a boiler furnace comprising a combustion chamber,of a bafHe depending from the top of the combustion chamber and uniting with the walls of the combustion chamber to provide a U-shaped path of flow for the burning fuel and products of combustion., one leg of which is of `smaller cross section in its upper portions than in its lower portion, and provisions for supplying pulverized fuel and air for the combustion in suspension of the fuel to the combustion chamber at the top of said one leg of said path, said one leg being so elongated that combustion is largely `completed therein.

2. The combination in a boiler furnace comprising a combustion chamber having vertical side and end walls,l of a baille depending from the top oi the combustion chamber and larger in horizontal cross section at its top than at its bottom and' forming with the combustion chamber walls a U- shaped path of flow for the burning fuel and products of combustion. and provisions for suppl \-'ing pulverized fuel and air for the combustion in suspension of the fuel, to the combustion chamber at the tcp of one leg of said path` said one leg being so elongated that combustion is largely Completed therein.

3. The combination ina boiler furnace comprising a combustion chamber and a baille depending from the top of the combustion chamber and formino with the combustion chamber walls a U-snaped path of ilow for the burning fuel andproducts of combustion smaller in horizontal cross section in the upper portion of each leg than at' lower levels. and provisions for-supplying pulver if-:cd fuel and air for the combustion in sispension of the fuel, to the combustion cham-` ber atthe top of one leg of said path, said one leg being so elongated that combustion is largely completed therein.

4. The combination in a boiler furnace` comprising a combustion chamber, of a baille depending from the top of the combustion chamber and uniting with the walls of the combustion chamber to provide a U-shaped path of flow for the, burning fuel and products of combustion, provisions for supplying pulverized fuel to the combustion chamber at the top of one leg of said path, and provisions for supplying air for the combustion in suspension of the fuel to said one leg, through saidbailie.

The combination in a boiler furnace comprising a combustion chambeigo'f a baille depending from the top of the combustion chamber and uniting with the walls of the combrstion chamber to provide a U-shaped path oL flow for the burning fuel and products of combustion, and provisions for supplying pulverized fuel and air for its combustion in suspension to the combustion chamber at the top ot' one leg of said path, said provisions including air supply ports opening into said one leg through said baille.

6. The combination in a boiler furnace comprising a combustion chamber and the outer wall thereof. of a baille depending from the top of the combustion chamber and forming with the latter a U-shaped path ofv ilow for the burning fuel and products of combustion. provisions for supplying fuel and air for its combustion to the combustion chamber at the top of one leg of said path, said provisions including air supply ports opening into the combustion chamber through said baille andthrough the portion of said Wall opposing said baille.

7. In combination, a boiler furnace comprising a combustion chamber in which pulverized fuel is burned in suspension, and a refractory baille depending from the top of the combustion chamber and forming with the latter a U-shaped path of flow for the burning fuel and products of combustion and having boiler heating surface elements arranged on its outer sides.

8. The combination in va boiler furnace comprising a combustion chamber, of a bail'le depending from the top of the combustion chamber and uniting with the walls of the combustion chamber to provide a U-shapcd path of flow for the burning fuel and products of combustion and comprising tubes inp corporated in the baille at its sides and forming a part ofthe boiler heating surface and means for supplying powdered coal and air for its combustion at the upper end of one leg of said U-shaped path.

9. The combination in a boiler furnace comprising a combustion chamber, of boiler heating surface comprisingl a steam and water space at `the top of said chamber and a depending baille comprising a central set of tubes connected at their upper end to the underside of said space, two other sets of tubes, one set at each side of and horizontally displaced from said central tubes, the tubes in said other sets being connected at their upper ends to said space, and connections between the tubes in said central set and the tubes in the side sets at the lower ends of the tubes.

10. The combination in a. boiler` furnace comprising a combustion chamber, of boiler heating surface comprising a steam and water drum at the top of said chamber and a baille depending from said drum and comprising a central set of tubes connected at their upper ends to the underside of the drum, two other sets of tubes, one at each side ot', and horizontally displaced from said central tubes. the tubes in said side sets being connected at their upper ends to the steam and water drum at the sides of the latter, connections between the tubes in said central set and the tubes in the side sets at their lower ends, and refractory material closing the spaces between the central tubes and said side sets.

11. The combination with a boiler furnace comprising a combustion chamber ith ash pockets at its lower end, of a baille depending centrally from the top of the combustion chamber and uniting with the walls of the latter to form a U-shaped path of flow for the burning `fuel and products'of combustion, provisions for supplying fuel in `the llO form of powdered coal and air for its combustion to the combustion chamber at the top of one` leg of sai-d path, and provisions for withdrawing products of combustion from the combustion chamber at the top of the other leg of said path, and boiler heating surface comprising a screen of water tubes extending across the combustion chamber below said baffle and above said ash pockets.

12. ln apparatus for burning pulverized coal, the combination of a combustion chamber provided with an outlet, draft creating means, a boiler heating surface within said chamber' assisting in defining the combustion space thereof, means for introducing the fuel into the combustion chamber at a velocity substantially greater than the outlet flow of products of combustion, and means for creating a relatively cool Zone in the lower portion of the combustion chamber for cooling the gravitating refuse substantially below the slagging point,

13. 1n app-aratus for burning pulverized coal, the combination of a combustion chamber provided with an outlet, draft creating mea-ns, a boiler within said chamber assisting in defining the combustion space thereof, means for introducing the fuel into the combustion chamber at a velocity substantially greater than the outlet flow of products of combustion, means for admitting air for combustion at a point near where the fuel is admitted, said combustion chamber being relatively contracted in cross sectional area whereby prompt admixture and combustion is brought about by the velocity of the fuel and flame stream resulting from the contraction in area, and means for creating a relatively cool zone in the lower portion of the combustion chamber for cooling the gravitating refuse substantially below the slagging point. Y 14. ln apparatus for burning pulverized coal, the combination of a substantially lll-shaped combustion chamber provided with an outlet, draft creating means, a boiler within said chamber assisting in defining the `combustion space thereof, means for introducing the fuel into the combustion chamber ata velocity substantially greater than the outlet flow of products of combustion, means whereby a. flow of air for combustion is induced into the combustion chamber substantially approximate to the entering fuel, said combustion chamber being relatively contracted in cross sectional area whereby prompt 'admiXture and combustion is brought about by the velocity of the fuel and flame stream resulting from the contracting in area, and mea-ns for creating a relatively cool Zone in the lower portion of the combustion chamber for cooling the gravitating refuse substantially below the slagging point.

15. The vcombination in a boiler furnace comprisinga ,combustion chamber, of a susreageer pended bame having a free lower end and comprising a tubular metallic framework formin (a part of the boiler heatino surface, and refractory material supported by said framework.

16. The combination in a boiler furnace comprising a combustion chamber, of a baille depending from the top of the combustion chamber and forming with the latter a U-shaped path of How for the burning fuel and products of combustion, and provisions for supplying fuel and air for its combustion to the combustion chamber at the top of one leg of said kpath, said provisions including air supply ports opening into the combustion chamber through said baHie and through the opposing wall of the combustion chamber and a common air supply source connected to all of said ports.

17. rlfhe combination in a boiler furnace comprising a combustion chamber, of a baffle depending from the top of the combustion chamber and forming with the latter a U- shaped path of flow for the burning fuel and products of combustion, and provisions for supplying fuel and air for its combustion to the combustion lchamber at the top of one Btl leg of said path, saidprovisions including air supply ports opening into the combustion chamber through said baffle and through the opposing wall of the combustion chamber and a common source of preheated air connected to all of said ports.

18. A heater comprising a fire chamber in which intense heat is developed and a communicating tube chamber at one end thereof, heat absorbing surfaces in said tube chamber and intermediate refractory wall between the tube chamber and fire chamber, uncovered tubes disposed upon the roof of the lfire and tube chambers and upon the side walls of the tire chamber exposed to the direct radiant heat of the fire.

19., A heater comprising a fire chamber in which intense heat is developed and a communicating tube chamber, heat absorbing surfaces in said tube chamber, an intermediate refractory wall between the tube chamber and fire chamber, and uncovered connected tubes disposed upon the roof of the fire and tube chambers and upon the side walls of the fire chamber exposed to the direct radiant heat of the lire, said first-mentioned heat absorbing means in the tube chamber adapted to receive substantially only convection heat.

20. A. fluid heater comprising a combustion chamber, a tube chamber and an intermediate refractory wall between the'tube chamber and the combustion chamber but shaped to provide a communicating port between said chambers, means for effecting the combustion of fuel in said combustion chamber to develop 4intense heat in said chamber, fluid containing heat absorbing conduits lining the major portions of the side walls and roof of said comlCl bustion chamber and a horizontally disposed wall of said tube chamber adjacent said port, and a plurality of separategroups of conduit elements located in said tube chamber and adapted to receive substantially only convection heat from the heating` gases passing into the tube chamber from said combustion chamber.

, 21. A fluid heater comprising a combustion chamber, 'a tube chamber, a refractory wall between lower portions of the tube vand fire chambers which are in communication with one another above said wall, means for effecting the combustion of fuel in said combustion chamber to develop intense heat in said chamber, fluid containing heat absorbin conduits lining the major portions of the si e walls of said combustion chamber and the roof of each of said chambers and conduit elements located in said tube chamber and adapted to receive substantially only convection heat from the heating gases passing into the tube chamber from said combustion chamber.

22. The method of burning powdered coal and utilizing the heat thereby generated, which comprises injecting the coal and carrying air into the initial end of an elongated transversely restricted iame path, burning the coal in suspension in a portion of said path of a cross section increasing in accordance with the initial increase in the volume of the gaseous products of combustion as combustion proceeds, securing intense combustion by effecting a rapid admixture of the burning coal and carrying air mixture with additional air for combustion in an initial portion of said path, 'directing the gaseous products of combust1on through a subsequent portion of said path of a cross section decreasing in accordance with the decrease in volume of said gaseous products of combustion as the latter cool, and absorbing relatively large amounts of radiant heat from said path and cooling the solid residue of the coal reaching the outer sides of said path by absorbing radiant heat at distributed points along the initial and subsequent portions of said path. y

23. The method of burning comminuted fuel and utilizing the heat thereby generated, whichcomprises injecting the fuel and carrying air downwardly into the initial end of an elongated transversely restricted flame path, burning the fuel in suspension in a portion of said pathof a cross section increasing in accordance with the initial increase in the volume of the gaseous products of combustion as combustionproceeds, securing intense combustion by effecting a rapid admixture of c the burning fuel and carrying air mixture with additional air for combustion in an initial portion of said path, directing the gaseous products of combustion upwardly through a subsequent vertical portion of said path, and absorbing relatively large amounts of radiant heat from said path and cooling the solid residue of the fuel reaching the outer sides of said path by absorbing radiant heat which comprises injecting the coal and carrying air downwardly into the initial endl of an elongated transversely restricted U- shaped flame path, burning the Acoal in suspension in a portion of said path of a cross section increasing in accordance with the initial increase in the volume of the gaseous products ,of combustion as combustion proceeds, securing intense combustion by effecting alrapid admixture of the burning coal and carrying air mixture with additional air for combustion in an initial portion of said path, directing the gaseous products of combustion upwardly through a subsequent portion of said path of a cross section decreasing in accordance with the decrease in volume of said gaseous products of combustion as combustion proceeds, and absorbing relatively large amounts of radiant heat from said path and cooling the solid residue of the coal reaching the outer sides of said path by absorbing radiant heat at distributed points along the initial and subsequent portions of said path.

25. The combination with a combustion chamber shaped to form an elongated'tlame path having separated end portions progressively tapering in cross section from an intermediate portion, of means for supplying powdered coal and air for its combustion to said chamber adjacent one end of said path and for withdrawing products of combustion from the combustion chamber at the opposite end of the path as required to maintain a relatively high iame velocity through all portions of said path, heat utilizing apparatus at the walls of said combustion chamber absorbing radiant heat from said chamber, and means for withdrawing heat from said apparatus and thereby maintaining the latter at a temperature substantially below the average gas temperature in the combustion cham er.

26. Pulverized fuel burnin apparatus comprising a combustion cham er having a pulverized fuel inlet and an outlet for products of combustion, said chamber being proportioned to provide a iow of burning gases and products of combustion therethrough at a substantially constant velocity, and means for introducing comminuted fuel and carrying airthrough said fuel inlet at a velocity su stantlally greater than the gas velocity through said outlet.

27.l Pulverized fuel burning apparatus com rising a substantially U-shaped combustlon chamber having a pulverized f llel inlet and an outlet for products of combustion,

said chamber being proportioned to provide a flow of burning gases and products of combustion therethrough at a substantiall constant velocity, and means for intro ucing comminuted fuel and carrying air through said fuel inlet at ay velocity substantially greater than the gas velocity through said outlet. I

28. Pulverized fuel burning apparatus comprisin a substantially U-shaped combustion cham er having a pulverized fuel inlet at one end of one leg and an outletfor products of combustion at the opposite end of the other leg of said chamber, said chamber being varied in cross-sectional area to provide a flow of burning gases and products of combustion therethrough at a substantially constant velocity, means for introducing comminuted fuel and carrying air through said fuel inlet at a velocity substantially greater than the gas velocity through said outlet, and means for absorbing substantial amounts of radiant heat from said chamber.

29. A high pressure water tube boiler comprising a combustion chamber, means for burning comminuted fuel in suspension in said chamber, radiant heat absorbing boiler heating surface in said chamber, and a steam and water space adjacent and connected to said boiler heating surface and formed by a group of interconnected horizontal drums of relatlvely small diameter, said drums being arranged to have the normal water level in said boiler pass through one or more, and above and below others of said drums.

30. The method of burning comminuted fuel at high temperatures which consists in injecting a stream of comminuted fuel and carrying air into a combustion chamber shaped to provide an elongated transversely restricted fla-me path, preheating additional air for combustion, and supplying the additional air for combustion at a substantial velocity to the chamber at opposite sidesl of said stream in an initial portion of the length of said path and entering said path at a substantial angle to the stream to thereby effect rapid mixture and combustion.

31. A fluid heater comprising a combustion chamber substantially rectangular in horizontal cross section and a tube chamber at one end thereof and separated therefrom by an intermediate refractory wall, a heating gas passage connecting said chambers at the upper end of said wall, means for burning fuel at high temperatures in said combustion chamber, and fluid heating conduits for absorbing the heat generated comprising a multiplicity of tubular conduit elements arrangedin proximity to the side walls and roof of said combustion chamber and substantially enclosing said combustion chamber, said elements being exposed to and arranged to absorb radiant heat from the burning fuel, and a plurality of tubular conduit meedoen.

elements in said tube chamber adapted to receive .only convection heat from the products off/combustion passing through said heating gas outlet.

82. A fluid heater comprising a combustion chamber substantially rectangular in horizontal cross section and a tube chamber at one end thereof and separated therefrom by an intermediate refractory wall, a heating gas passage connecting said chambers at the upper end of saidwall, means for burning fuel at high temperatures in said combustion chamber, and iuid heating conduits for absorbing the heat generated comprising a multiplicity of tubular conduit elements arranged in proximity to the side walls, roof and refractory Wall of said combustion chamber and substantially enclosing said combustion chamber, said elements being directly exposed to and arranged to absorb radiant heat from the burning fuel, and a plurality of tubular conduit elements in said tube chamber adapted to receive only convection heat.

83. rl`he combination with a combustion chamber having a boiler, tubes of which define combustion space, and means for admitting fuel in finely divided form with primary air for combustion, of means forming a space 'behind said" tubes, means for admitting secondary air for combustion to the space between wall and tubes, and means for preheating said air, the said tubes being spaced apart to provide a pluralityy of air inlets to said combustion chamber.

34. The combination4 with a combustion chamber having a boiler, tubes of which define combustion space, and means for admitting fuel in finely divided form with primary air for combustion, of a wall spaced from said tubes, means for admitting secondary air for combustion to the space between wall and tubes and means for preheating such air, the said tubes being spaced apart to provide a plurality of air inlets to said combustion space.

35. The combination in a steam generator having means for admitting fuel in finely dic vided form with primary air for combustion, of tubes defining combustion space arranged for the admission of further air therebetween tothe combustion space, and means for supplying such further air to the region behin the tubes.

36. The combination in a-steam generator having means for admitting fuel in finely diy vided form with primary air for combustion,

of a plurality of substantially vertical tubes connected into the circulation of the boiler and defining combustion space, means forming a space behind the said tubes and means for admitting further air to said space, the tubes being spaced apart to provide a plurality of air openings therebetween, said openings extending substantially from top to bottom of the combustion space.

tion with a portion of said stream in which combustion 1s substantially complete.

38. A. Water-tube boiler having radiant heat absorbing tubes and convection heat absorbing tubes forming a single circulatory system, a pre-furnace, one Wall of said preurnace being lined with said radiant heat absorbing tubes, saidpre-furnace having an unrestricted outlet therefrom, means for introducing ignited combustible gasesand air into said pre-furnace, and a main furnace of greater volume than said pre-furnace in communication with said convection heat absorbing tubes and with said pre-furnace through said outlet, the ignited gases and air expanding in said main furnace in their passage from the pre-furnace to said convection heat absorbin tubes.

39. furnace comprising an entrance throat disposed above and leading to a main chamber of substantially greater cross-sectional area than said entrance throat, water carryino' tubes forming a part of the defining Walls of said throat and extending into said main chamber, a water cooled outlet from said main chamber, and means for directing fuel and air into said throat and discharging the products of combustion through said water cooled outlet.

Signed at city of New York in the county of New York and State of New York this 12th day of January A. D. 1923.

JOHN E. BELL. 

